I found a discussion over brunch entertaining.
Apparently women sniffed teeshirts worn 2 days by males. Women preferred the shirts belonging to genetically dissimilar men. These are the good men because they ensure better MHCs in offspring. Unfortunately, the women on oral contraceptives preferred genetically similar men. Yeah. The latter women would prefer their brother, son, or father (all sharing 1/2 her genes) to any other men. The feared scenario is women marry men satisfying their preference for genetically similar men and in preparing to have children suddenly find their husbands revolting.
Our mothers were on to something when told us to always smell nice. Preventing women on birth control from smelling who we really keeps us from getting judged down inappropriately. Well, really the game we play is not letting the other side have too much information.
P.S. The same study almost found significance to single women preferring genetically similar men. That really would make news.